The invention relates generally to clips used in wastewater treatment tanks, such as that disclosed in U.S. Pat. No. 5,490,935, shown in FIG. 1, having a central conical clarifier 100 and a plurality of droplines 102 encircling the clarifier. In such systems, air is generally pumped through the droplines and into the wastewater in the tank in order to foster the growth of aerobic bacteria.
The conical clarifier 100 usually has a lip 104 at its upper edge. This lip 104 rests on a series of brackets 105 placed on the tank walls. A typical bracket used is an “L” shaped bracket. One leg of the “L” attaches to the tank walls so that the other plate extends perpendicularly from the walls. The clarifier lip 104 rests on the plate of the “L” bracket that extends from the wall.
The droplines 102 in such a system generally extend downwardly from a circular distribution manifold, although other configurations are used, and the manifold is connected to an air source. The entire air distribution system is frequently comprised of ½ to ¾ inch PVC pipe. The droplines 102 are generally pipes with one or more openings near the end of the pipe distal from the distribution manifold. The air distribution manifold is supported by the “L” bracket. Each “L” bracket contains a hole which is sized to fit a dropline, so that the droplines extend down through an “L” bracket to near the bottom of the tank.
Pumping air through the droplines causes them to oscillate. Oscillations can cause damage to the droplines, particularly near the fittings which connect the droplines to the distribution manifold. The oscillations can be reduced by having the distal end of the drop tubes supported against the tank wall with brackets or retainers 150. However, these brackets are located in the fluid filled volume of the treatment tank and if the through-the-wall attachment fixtures are used, leakage through the bracket attachment points can be a problem. To avoid leakage, the retainer 150 can be welded or “glued” to the inner tank wall. However, welding the retainer to the tank wall can also create a weak spot in the tank wall which can potentially lead to a leak. If adhesives are used to attach the fitting to the tank wall, there is a risk that, over time, the adhesive will give way and become ineffective, potentially resulting in damage to the system.
U.S. Pat. No. 5,879,550 (incorporated by reference) discloses a wastewater treatment clip designed to reduce the amount of oscillation to the droplines. That clip consists of generally a “U” shaped bracket having two parallel main plates separated by a bracing plate. The two parallel main plates each contain an opening sized to accommodate a dropline. The clip attaches either to the inside wall of the wastewater treatment tank or hangs on the upper lip of the tank. In either instance, the clip attaches above the waterline and thus avoids potential problems associated with puncturing the tank wall below the waterline. In use, the distribution manifold rests on the upper parallel main plate of the “U” bracket and a dropline extends downwardly from the manifold through the twin openings in the “U” bracket. The two parallel main plates of the “U” bracket provide additional support for the droplines and assist in controlling the oscillations of the droplines.
Experience has shown that the “U” shaped clip reduces oscillations. However, the droplines undergo stress near the holes in the “U” shaped clip, and the problem is aggravated when the wastewater treatment tank or its aeration system becomes unleveled or tilted. In this instance, the dropline air discharge openings are not level and air passing through the manifold to the droplines will have a tendency to preferentially discharge through the dropline which is “higher” (closer to the ground surface) than the other drop lines. As a result, a larger volume of air migrates through the higher dropline, and causes increased vibration and oscillation for this high dropline. This increased oscillation and vibration often results in cracks, fractures, and breaks in the droplines at the location of the holes in the parallel main plates and at the point of connection between the droplines and the circular feeder.